Ships for transporting liquid cargoes



N 1966 J. J. CHICO GARATE 3,288,093

SHIPS FOR TRANSPORTING LIQUID CARGOES 2 Sheets-Sheet 1 Filed March 2, 1964 LNVENTOR JUAN JOSE CHICQ GARATE 2% viii: BY

AGENT Nov. 29, 1966 J. J. CHICO GARATE 3,288,098

SHIPS FOR TRANSPORTING LIQUID CARGOES Filed March 2. 1964 2 Sheets-Sheet 2 FIG. 7A

@270 FIG. 8

20/ FIG. 7B

Q Q QQQ Q l0 I5 1 1 I5 INNENTOR JUAN JOSE CHICO GARATE AGENT United States Patent 3,288,098 SHIPS FOR TRANSPORTING LIQUID CARGOES Juan Jos Chico Garate, Ibiza 66-1D, Madrid, Spain Filed Mar. 2, 1964, Ser. No. 348,732 18 Claims. (Cl. 11474) The present invention relates to the economic transport of liquid cargoes by sea and to ships suitable to this end. In particular, the invention relates to ships having a thin skin, which is preferably sectioned, for transporting liquid cargoes.

The purpose of the system described is to achieve an economical transport of liquid cargoes by sea, and at a lower price than with the ships used today.

This result is obtained basically by means of a principle which enables to reduce substantially the stresses produced in a ship structure, and therefore in the corresponding steel thicknesses.

This principle consists, on the one hand, in bringing the liquid cargo under a pressure which balances the external pressure, in such a way that the sides and the bottom of a ship do not have to withstand any transverse bending moment, and, on the other hand, in building these parts of a hull with enough flexibility so as to be deformed in such a way that the transverse bending moment will not exceed a small value requiring, as mentioned, very small thickness.

To achieve this pressure balance with the ship in ballast, an equivalent volume of sea water is admitted inboard according to the present invention, for which the hull sides are provided with appropriate means-holes or valvesaffording the water inflow.

Also when the ship is only partly loaded, water is admitted inboard, into the cargo space, separating it from a liquid cargo by means of flexible membranes. In certain cases of unmiscible liquids, the membranes can be omitted.

The deck, on the contrary, is given suflicient stiffness to support pipe ducts, inlets and other necessary inlet and discharge devices, and also to transmit the propulsion and working stresses, etc.; notwithstanding, in certain cases the deck can be allowed limited longitudinal flexibility, as will be explained later.

In order to limit the longitudinal bending moment, the principle of a semi-submerged ship is adopted. In

still waters, only a small forecastle and a small quarter-,

deck emerge, suitably closed and made watertight, and which are provided with all the necessary anchoring and mooring gear, working gear, navigational instruments, ventilating and life-saving equipment, etc., all suitably located and secured.

The small emerging volumes reduce the longitudinal bending stresses produced by the waves which act on the hull; these volumes, therefore, require only small scantlings and structural materials.

In certain cases, when specially treating large ships, the hull may be provided with a sufficient longitudinal flexibility in order that the ship can be deformed when on waves, thus reducing the immersion of the forecastle and the quarter-deck, and also the corresponding longitudinal bending moment.

The invention will now be described in more detail with reference to the accompanying drawings, wherein FIG. 1 is a schematic transverse section of a ship according to the present invention;

FIG. 2 is a longitudinal section of aggregate frames and skin used in the ship according to FIG. 1;

FIG. 2A is a partial perspective view of the skin and frame appearing in FIG. 2;

FIG. 2B is a cross-sectional view, taken along line 2B2B of FIG. 2A;

FIG. 2C is another cross-sectional view, taken along line 2C2C of FIG. 2B, and similar to FIG. 2;

FIGS. 3 through 5 schematically illustrate various stability and buoyancy conditions of the novel ship;

FIG. 6 is a schematic side elevation of the ship when floating in still waters;

FIG. 7 is an elevational side view, similar to that of FIG. 6, of a ship when deformed, and having an extensible or articulated skin;

FIGS. 7A and 7B are respective side and bottom views of the inventive ship, having bulkheads at the fore and aft sections of the ship;

FIG. 8 is a schematic sectional view of a deformed ship hull;

FIG. 9 is a transverse sectional view of a joint for the ships skin;

FIG. 10 is a longitudinal section of a skin assembly with plural sections;

FIG. 11 is a side elevation of a riveted skin section;

FIGS. 12 and 13 are respective frontal and sectional views of an elastic washer suggested in connection with the attaching rivets;

FIG. 14 is a partly sectional view of a valve used in connection with the inventive ship;

FIG. 14A is a top view of the valve of FIG. 14, looking toward the ships skin; and

FIG. 14B is a view similar to FIG. 14A, taken along line 14B14B of FIG. 14, showing the valve spindle alone.

In FIG. 1, showing a ship according to the invention, 1 is a deck having suitable transverse stiffness; numeral 2 denotes void spaces provided in order to insure suflicient buoyancy to the whole ensemble. When cargoes of diverse densities are carried, they can be partly flooded, in order suitably to adjust the overall buoyancy. An outer skin 3 of the hull may be made with very light framing or even without framing, and may be provided with adequate flexibility in order to reduce the bending stresses bearing on them.

Void buoyancy spaces 4 can be arranged in order to provide the skin 3 with a displacement equal or approximate to its weight, thus reducing even further the bending stresses. A membrane 5 is provided inside the skin for preventing-contact between the liquid cargo and the sea water, but transmitting the pressures occurring between both of them. The skin 3' is provided with holes (not shown) for the inward flow of sea water, either permanently opened or closed by valves which have to be opened when the ship is charging or discharging.

The views of FIGS. 2A, 2B and 2C are self-explanatory and show the elements (skin 3, buoyancy spaces 4) as shown in FIGS. 1 and 2, together with a framing 5a. In all the figures, the ship has generally been designated by numeral 20.

Transverse structural slrength.According to this principle the skin is subjected only to small stresses, arising from the difference of density between the liquid cargo and the sea water on respective sides of the membrane 5,

besides the dynamic stresses, also considerably reduced as compared to stresses corresponding to a conventional ship.

A stability in form can be obtained by means of the light frames a, a free deformation can also be permitted, eliminating the frames. In this case the outer skin 3 could be made of very small thickness, and there must be adopted a flexible coupling system between the extreme forward and rear sections, which necessarily must be stiff, and the outer skin of the central ship section, intended to carry the cargo.

If light frames are used, they can be assembled so as to form a thin undulated plate 5a (FIG. 2) spot-welded to the skin 3, leaving the buoyancy spaces 4 sufficient to balance the displacement and the weight of the whole structure FIGS. 2A, 2B and 2C show the undulated plate frame 5a.

If the assembly so devised has a certain transverse strength constant, and is constrained at both ends, for withstanding a constant transverse bending moment, it will take a circular form, with stability tending to maintain it, and opposing the forces tending to deform or buckle the assembly.

If the aforementioned openings in the skin 3 are closed, and the cargo inside the membrane 5 or the plate 5a is subjected to a small overpressure, an approximately circular section can be maintained, if the weight of the skin 3 is small. In such a case the ship ends must be closed by means of bulkheads withstanding this overpressure. If these bulkheads have a nearly spherical form, they could also be made with very small thickness, being subjected only to (two dimensional) extension stresses, and not to bending stresses.

Transverse stability.If in the ship section intended for the cargo the displacement balances the weight, that is to say, this section does not contribute to buoyancy, stability will be neutral (FIG. 3). If a small buoyancy excess is adopted (the deck 1 emerges to a small degree) a righting couple will appear (till the inclination in which the centre of buoyancy lies is in the same vertical as the center of gravity of the emerging wedge, as illustrated in FIG. 4).

If the buoyancy excess is concentrated at both sides (FIG. 5), the righting couple will be maintained up to inclinations very near over 90. To these righting couples will have to be added, of course, the couples corresponding to the fore and after emerging sections. These will be the couples providing the main part of the static and dynamic stability.

Let us suppose the ship is floating in still waters 6 (FIG. 6), and only the parts shown in the figure emerge, that is, a small forecastle and a small quarter-deck, as explained before. With an adequate distribution of weights and buoyancy in the forward and after sections, it can be secured that the bending moment will nearly cancel out in still waters. In both FIGS. 6 and 7, respective fore and aft bulkheads 17b and 17a are shown. They also appear in FIGS. 7A and 7B, in respective side-elevational and bottom views of the ship 20. As schematically shown, these are preferably spherical bulkheads attached to the hull of substantially semi-circular cross-section.

Let us now suppose a wave of a length equal to that of the ship, in the two conditions usually considered, that is, sagging 7 and hogging 8. In the sagging condition, a central part 9 of the ship, dashed in FIG. 9, would emerge from the water, with a volume equivalent to the submerged parts of the forecastle and quarter-deck (which may be almost wholly submerged).

Maximum bending moment would appear near the midship section (the section corresponding to the center of gravity of the part 9), and its value would be the product of the distance between this section and the center of gravity of the submerged part of the forecastle or quarter-deck, times the displacement of the corresponding submerged part. This displacement can be made as small as desired, within the limits considered as necessary for the sake of ship safety.

The bending moment can be, therefore, very small thus requiring very light scantlings for the ships structure.

For ships of very great lengths, it may be admitted that the ship structure can also be longitudinally deformable in such a way that the bending moment will be capable of producing a deformation which maintains the forecastle and quarter-deck partly emerging at all times. Then, the volume of the parts submerged by the wave would be smaller than in the case of a rigid ship, and therefore the bending moment would also be smaller, which acts upon the ship structure (FIG. 7).

For this it would be necessary to make the ships outer skin 3 from an easily extensible or stretchable material, or articulated with separate sections 10 (FIG. 7) in such a way that only the deck 1 would have an appreciable bending stiffness. Consequently, adequate bending would be acquired which, in ships of great length, can be sufficient to secure that the stresses in the ship structure will be maintained within small values, thus requiring only small scantlings.

In the hogging condition usually considered (line 8 of FIG. 6), that is, with the maximum wave height near the midship, the section 9 will be subject to practically no bending moment. The effect of the wave height on the midship section would be to increase the pressure as much outside as inside, practically without producing additional stresses in the ship structure. In FIG. 7, 1 denotes the force of buoyancy acting on the forecastle, while d identifies the distance between the vertical lines passing through the center of buoyancy of the forecastle and the midship section, respectively.

On the deck 1 of these ships can be suitably disposed all the devices necessary for charge and discharge, since it may have at all times the suitable stiffness to bear all the piping, valves, inlets and outlets etc., needed; the piping, of course, must have the necessary flexibility.

The outer skin 3 can retain, within its flexibility, the form stability needed in order to achieve good hydrodynamic performance; the semi-circular form of the section as illustrated in FIGS. 1 and 35, is suitable to achieve the minimum wetted surface, without presenting too large rolling movements, since by its semi-submerged condition, the rolling exciting couples produced by the waves are lessened to a great extent.

Torsional structural strength-If the ship navigates in swelled seas, oblique to the waves, that is, a quarter from the bow or the stern, torsional stresses can arise on the hull and, in the case of a flexible deck, torsional deformation. If the forecastle and the quarter-deck are of small dimensions, the torsional moment acting upon the hull will not be great, but, notwithstanding, if the deck is flexible and the skin of very small thickness, stress concentrations and buckling could arise.

In order to avoid this, the elastic connections between adjoining skin joints 11 (FIG. 7) can be made in such a way that a relative sliding motion along the joint be allowed.

Thus, not presenting the skin 3 may resistance to torsion, the deck 1 will be free to deform, taking an approximately helicoidal form (indicated in FIG. 8 by superimposing different varying transverse sections of the hull) with its axis along the longitudinal middle line of the deck 1, thus coinciding with the rotational axis of the skin sections 10, if the form adopted for these sections is cylindrical, with semi-circular frames.

The displacement of the sections 10 along the joints 1 between them will allow the cylindrical sections of the skin to follow the deck deformation without producing shear stresses or buckling of the thin skin.

In order to obtain freedom of displacement between the skin sections, and longitudinal elasticity of the hull, a proceeding would be to make the joints 1 with longitudinally split tubes 12 (FIG. 9)-or tubular sections and fitting them into grooves provided along butts 13 of the skin sections 10 (FIG. 9). This joint 11 need not be watertight. The different sections 10, if constituted as explained in FIG. 2, will make an assembly as shown in FIG. 10.

In order that the attachment between the diflerent skin sections 10 and the deck 1 does not initiate for practical purposes, any shear stress acting upon the thin skin, the central part of this attachment could be made rigid, riveted or welded. In FIG. 11, rivets 14 are shown in the center of skin section 10. The extreme parts of this union, on the contrary, can be provided with a certain elasticity, for example, by means of elastic washers 16, in FIGS. 12 and 13 which do not require further explanation.

The quarter-deck must be adequately safeguarded against the wave onrush, suitably closed up to a safe height, and also provided with a properly designed breakwater, including also the navigating bridge, life boats and life-saving equipment, ship working gear, smoke outlet and ventilation inlets and outlets, running lights, signals, mast, etc. at a suitable height above sea level to offer the necessary safety, maintaining also a closed watertight volume suitable for safetys sake, but not too great in order to maintain the bending stresses at a low value.

As has been explained earlier, the skin 3 of the ship 29 may be provided with holes or openings for the communication of sea water into and out of the buoyancy spaces 4 (see FIGS. 1 and 2A). At these holes, valves 18 may be provided, a conventional form of which has been shown in FIGS. 14, 14A and 1413. The valves may be attached to the inboard side of the hull skin 3 and may have light springs and appropriate spindle members. Conventional manual means (not illustrated) may be provided for opening and closing the valves when the ship is being charged or discharged. The valves may also be provided so that they open when the outer and inner pressures are identical.

I claim:

1. A ship for the sea transport of liquid cargoes, comprising a hull formed by a thin skin, having an inherent buoyancy, a deck to which said skin is attached, flexible separating means within said skin and defining both an inner liquid cargo space and an outer buoyancy space between said separating means and said skin, separate from said cargo space, and means for admitting the sea water to said buoyancy space, with free communication between the latter and the outside, thereby subjecting said cargo space to at least the same pressure as that of the sea water, so as to minimize stresses acting on said hull.

2. A ship as defined in claim 1, wherein said skin is freely deformable, so as to lessen the static and dynamic stresses acting on said hull.

3. A ship as defined in claim 1, wherein said skin is made of a flexible and at least partly stretchable material, said deck has an appreciable rigidity to bending, and said means for admitting the sea water applies to said flexible skin a pressure slightly higher than that of said sea water on said hull, so as to impart stability to said hull.

4. A ship for the sea transport of liquid cargoes, comprising a hull formed by a very thin skin, having an inherent buoyancy, and defining an inner liquid cargo space, a deck of conventional construction to which said skin is attached, means for subjecting said cargo space to at least the same pressure as that of the sea water outside, so as to minimize the stresses acting on said hull, a central ship part with a very small buoyancy, a small forecastle and a small quarter-deck, thoroughly closed and watertight, and means for concentrating the buoyancy of the ship in the fore and after sections, so as to reduce and at least partly cancel out the longitudinal bending moments acting on the respective parts of said hull.

5. A ship as defined in claim 1, wherein said cargo space has at least two separate, closed sections.

6. A ship for the sea transport of liquid cargoes, comprising a hull formed by a very thin skin, having an inherent buoyancy, and defining an inner liquid cargo space, a deck of conventional construction to which said skin is attached, means for subjecting said cargo space to at least the same pressure as that of the sea water outside, so as to minimize the stresses acting on said hull, a small forecastle and a small quarter-deck, wherein said skin is provided with longitudinal flexibility for allowing deformation when subjected to long waves, so as to reduce the immersion of said forecastle and of said qua'rtendeck, and thereby the bending moments acting on said hull.

7. A seagoing liquid cargo vessel comprising a hull formed by at least two very thin skin sections and defining an inner liquid cargo space, a longitudinally flexible but transversely rigid deck to which said skin sections are attached, means for subjecting said cargo space to at least the same pressure as that acting on said hull, so as to minimize the stresses acting on said skin sections, and at least one transversal flexible joint between said skin sections for allowing at least limited sliding movement between said skin sections along said joint, and admitting of free torsional deformation when the vessel is running on oblique waves.

8. A vessel as defined in claim 7, wherein said skin sections have butts defining grooves along their contiguous edges, and said joint is constituted by a longitudinally split tube fitting into and engaging said grooves inside said hull.

9. A vessel as defined in claim 8, wherein said tube defines a buoyancy space communicating with the sea water, so as to balance the displacement and the weight of said hull.

10. A vessel as defined in claim 7, further comprising a light, substantially semi-circular framing for securing said skin sections.

11. A vessel as defined in claim 7, wherein said hull has a substantially semi-circular cross-section, Ifurther comprising substantially spherical bulkheads at the fore and after sections of the vessel, :for withstanding the overpressure to which the liquid cargo in said cargo space may be subjected.

12. A vessel as defined in claim 7, further comprising separating means between said hull and said cargo space, defining at least one buoyancy space, for balancing the displacement and the weight of said hull.

13. A vessel as defined in claim 12, wherein said separating means is constituted by a flexible membrane preventing contact between the liquid cargo in said cargo space and the sea water, but transmitting pressures occurring between both of them.

14. A vessel as defined in claim 12, wherein said separating means is constituted by a thin undulated plate forming a light framing and secured intermittently to said skin sections, for preventing contact between the liquid cargo in said cargo space and the sea water.

15. A vessel as defined in claim 12, wherein said skin sections have holes for the passage of the sea water to said buoyancy space.

16. A vessel as defined in claim 15, further comprising at least one valve for said holes, to be opened when the vessel is charging and discharging.

17. A vessel as defined in claim 7, further comprising coupling means between said deck and said skin sections, including rigid coupling members in at least the central part of said skin sections, with freedom of displacement in the terminal parts thereof in the region of the joints with the adjoining skin sections, so as to avoid transmission to said skin sections of shear stresses arising from the torsion of said deck.

18. A vessel as defined in claim 17, wherein said coupling means further includes resilient coupling members in said terminal parts of said skin sections, for providing References Cited by the Examiner UNITED STATES PATENTS Keall 11472 X Smith 11477 Archer 114--77 Bnandon et a1. 11474 Denis et a1. 11474 8 3,067,712 12/1962 Doerpinghaus 11474 3,085,533 4/1963 Goryl et a1. 11474 3,087,454 4/1963 Lorentzen 11474 FOREIGN PATENTS 564,485 9/ 1944 Great Britain.

MILTON BUCHLER, Primary Examiner.

10 FERGUS S. MIDDLETON, Examiner.

T. M. BLIX, Assistant Examiner. 

1. A SHIP FOR THE SEA TRANSPORT OF LIQUID CARGOES, COMPRISING A HULL FORMED BY A THIN SKIN, HAVING AN INHERENT BUOYANCY, A DECK TO WHICH SAID SKIN IS ATTACHED, FLEXIBLE SEPARATING MEANS WITHIN SAID SKIN AND DEFINING BOTH AN INNER LIQUID CARGO SPACE AND AN OUTER BUOYANCY SPACE BETWEEN SAID SEPARATING MEANS AND SAID SKIN, SEPARATE FROM SAID CARGO SPACE, AND MEANS FOR ADMITTING THE SEA WATER TO SAID BUOYANCY SPACE, WITH FREE COMMUNICATION BETWEEN THE LATTER AND THE OUTSIDE, THEREBY SUBJECTING SAID CARGO SPACE TO AT LEAST THE SAME PRESSURE AS THAT OF THE SEA WATER, SO AS TO MINIMIZE STRESSES ACTING ON SAID HULL. 